He knew he was in trouble the morning he couldn't lift his head off the pillow. He awoke facedown, his skull feeling like a useless dead weight. A dark thought flashed through his mind: If he couldn't make the effort to pull himself up, he'd suffocate right there and then.

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Somehow, as if it was the hardest thing he'd ever done, he summoned the energy to move. He flipped over onto his back and thought, Jesus . . . that was a bit near.

Day by day, week by week, his condition had been steadily worsening. His often sleepless nights were spent shaking with anxiety, while his days, which he was finding harder and harder to make it through, were characterized by heavy drinking and self-sedation with marijuana. He found himself chain-smoking his unfiltered, lung-blackening Senior Service cigarettes one after another after another.

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Later, he would look back on this period and tell everyone that he'd almost had a nervous breakdown. From the outside, there appeared to be no "almost" about it.

For the first time in his life, he felt utterly worthless. Everything he had been since the age of fifteen had been wrapped up in the band. Now, even though he couldn't tell the world, that period of his life was almost certainly over.

It was as if he'd suddenly and unexpectedly lost his job, been made entirely redundant. He was twenty-seven and of no use to anyone anymore. Even the money he'd earned up to this point was no comfort, made no real difference. This was an identity crisis in extremis: Who exactly was he if he wasn't Beatle Paul McCartney?

On the mornings when he forced himself to rise, he'd sit on the edge of his bed for a while before defeatedly crawling back under the covers. When he did get out of bed he'd reach straight for the whiskey, his drinking creeping earlier and earlier into the day. By three in the afternoon, he was usually out of it.

"I hit the bottle," he admits. "I hit the substances."

He was eaten up with anger—at himself, at the outside world. He could describe it only as a barreling, empty feeling rolling across his soul.

Out of work and with nothing to distract him, he was tormented by ghosts from his past; they would rise up, whispering in his head, telling him that, in spite of everything he'd achieved, they knew he'd never really amount to anything. That he should have found a proper job in the first place, just as they'd always said.

He realized that up until this point he'd been a "cocky sod." And now there was this: the first serious blow to his confidence he'd ever experienced. Even when he was fourteen and the complications from a mastectomy had suddenly taken his mother's life, he had understood that this horrific event had been beyond his control. Somehow, now, in the depths of his muddied thinking, he was starting to believe that everything that was happening was nobody's fault but his own.

His wife of less than a year later said she had felt the situation was "frightening beyond belief." Within a matter of months, her new partner had gone from being a sparky, driven, world-famous rock star to a broken man who didn't want to set foot out of their bedroom. But even if Linda was scared, she knew she couldn't give up on Paul. She recognized that her husband was sinking into emotional quicksand, and she knew that it was down to her alone to pull him out before he went under for good.

"Linda saved me," he says. "And it was all done in a sort of domestic setting."

Their acreage was home to 150 to 200 sheep, which Paul learned to clip using hand shears, after which they sold the fleeces to the Wool Marketing Board. Already leaning toward vegetarianism, they balked at the notion of killing their lambs, although they were forced to send some off to market when the numbers grew too high. They tried to separate the ewes from the rams, but sometimes one of the male sheep would enthusiastically spring over the fence. In time, they had six horses, including the retired racer Drake's Drum, bought for Paul's father, Jim, and a former winner at Aintree, alongside Honor (Paul's), Cinnamon (Linda's), and three ponies, Sugarfoot, Cookie, and Coconut.Revving up a generator, Paul put together an ad hoc four-track recording facility in High Park's rickety lean-to, which he named Rude Studio. It was in here, gently encouraged by Linda, that his songwriting slowly began to return to him, as he effectively used music as therapy to alleviate his depression. "She eased me out of it," he remembers, "and just said, 'Hey, y'know, you don't want to get too crazy.' "Paul shied away from admitting that there was a strong autobiographical element to some of these new compositions, but his protestations rang hollow. The lyrics of "Man We Was Lonely" speak of how his and Linda's self-imposed exile was not as idyllic as it outwardly seemed, that their spirits had been low, but, under the comfort blanket of domesticity, their positivity was returning.

"Every Night," a song he'd first begun messing around with during the Let It Be sessions, was more confessional still—its singer painting a grim picture of a routine involving getting wasted and struggling to drag himself out of bed. The chorus, as was increasingly becoming a McCartney trait, pledged his devotion to Linda. As a song, it was a deceptively breezy affair. While elsewhere Lennon was screaming his pain, it was typical of McCartney to mask his with melody. Only if you listened closely would you really be able to detect the songwriter's anguish.

As Paul seemed to stabilize, the McCartneys settled into a daily routine, riding their horses across the land or taking sheepdog Martha for long walks. They drove into Campbeltown in their Land Rover, which they'd nicknamed Helen Wheels, the Beatle becoming a regular sight wandering around in his Wellies and sheepskin-lined brown leather jacket. In the evening, he would light the fire while Linda cooked, and then Paul would step into Rude to work on songs. At night, they would cuddle up, get stoned, and watch TV. "We were not cut off from the world," said Linda. "We were never hermits."

In addition, to playfully distract Paul from his troubles, there were the children to look after: the newborn Mary and Linda's child from her first marriage, shy Heather, only six. For the kids, High Park was a cross between a playground and a junkyard. As soon as she began to walk, Mary was free to toddle outside, through its abandoned gypsy encampment–like clutter of scrap wood, sheets of corrugated iron, and teetering log piles (noting incredulously as an adult that she'd effectively been brought up in a "lumber yard").

It was a messy scene but, for McCartney, one filled with increasingly frequent spells of happiness. Nevertheless, in a corner of his mind, knowing that there was a Beatles-shaped storm brewing back down in London, Paul was still plagued with unease.

It didn't help that everyone was arguing about whether or not he was dead...